What is the management approach for a 60-year-old male with diabetic ketoacidosis (DKA), a history of lung cancer, and smoking?

Management of Diabetic Ketoacidosis in a 60-Year-Old Male with Lung Cancer

Begin immediate fluid resuscitation with isotonic saline at 15-20 mL/kg/hour (approximately 1-1.5 L in the first hour), followed by continuous IV regular insulin at 0.1 units/kg/hour once serum potassium is ≥3.3 mEq/L, while identifying and treating precipitating factors including infection and ensuring SGLT2 inhibitors are discontinued if present. 1, 2

Initial Assessment and Diagnostic Workup

Obtain the following laboratory tests immediately:

• Plasma glucose, serum ketones (preferably β-hydroxybutyrate), electrolytes with calculated anion gap, arterial or venous blood gas, blood urea nitrogen, creatinine, osmolality 1, 2
• Complete blood count with differential, urinalysis with urine ketones, electrocardiogram 1, 2
• Given his lung cancer history, obtain bacterial cultures (blood, urine, throat) if infection is suspected, as infection is a common DKA precipitant 1, 2
• Check for recent initiation of SGLT2 inhibitors, which can cause euglycemic DKA and must be discontinued immediately 2, 3

DKA is confirmed when: glucose >250 mg/dL (though euglycemic DKA can occur), pH <7.3, bicarbonate <15-18 mEq/L, and elevated ketones. 2, 4

Critical Potassium Management Before Insulin

DO NOT start insulin if serum potassium is <3.3 mEq/L—this is an absolute contraindication that can cause life-threatening cardiac arrhythmias and death. 1, 2

If K+ <3.3 mEq/L:

• Continue isotonic saline but hold insulin 1
• Confirm adequate urine output, then aggressively replace potassium with 20-40 mEq/L in IV fluids (use 2/3 KCl and 1/3 KPO₄) 1
• Obtain electrocardiogram to assess for cardiac effects 1
• Recheck potassium frequently until ≥3.3 mEq/L before starting insulin 1

If K+ 3.3-5.5 mEq/L:

• Add 20-30 mEq/L potassium to each liter of IV fluid once urine output confirmed 1, 2
• Target serum potassium 4-5 mEq/L throughout treatment 2

Fluid Resuscitation Protocol

• Start with 0.9% normal saline at 15-20 mL/kg/hour for the first hour 1, 2
• Subsequent fluid choice depends on hydration status, electrolyte levels, and urine output 2
• When glucose falls to 200-250 mg/dL, switch to 5% dextrose with 0.45-0.75% saline while continuing insulin infusion—this prevents hypoglycemia while ensuring complete ketoacidosis resolution 1, 2
• Total fluid replacement should approximate 1.5 times 24-hour maintenance requirements 1

Insulin Therapy Protocol

Once K+ ≥3.3 mEq/L:

• Give IV bolus of 0.1 units/kg regular insulin 1, 2
• Start continuous infusion at 0.1 units/kg/hour regular insulin 1, 2
• Target glucose decline of 50-75 mg/dL per hour 1, 2

If glucose does not fall by 50 mg/dL in the first hour:

• Verify adequate hydration status 1
• If hydration acceptable, double the insulin infusion rate hourly until steady decline achieved 1, 2

Continue insulin infusion until DKA resolution regardless of glucose levels—do not stop insulin when glucose normalizes. 2

Monitoring Requirements

Check every 2-4 hours:

• Blood glucose (can check more frequently) 1, 2
• Serum electrolytes (especially potassium), blood urea nitrogen, creatinine, osmolality 1, 2
• Venous pH (typically 0.03 units lower than arterial pH) and anion gap 2
• Direct measurement of β-hydroxybutyrate in blood is preferred over urine ketones 1, 2

Bicarbonate Administration

Do NOT give bicarbonate if pH >6.9-7.0—multiple studies show no benefit in resolution time or outcomes, and it may worsen ketosis, cause hypokalemia, and increase cerebral edema risk. 2, 5

DKA Resolution Criteria

DKA is resolved when ALL of the following are met:

• Glucose <200 mg/dL 1, 2
• Serum bicarbonate ≥18 mEq/L 1, 2
• Venous pH >7.3 1, 2
• Anion gap ≤12 mEq/L 1, 2

Transition to Subcutaneous Insulin

Administer basal insulin (glargine or detemir) 2-4 hours BEFORE stopping IV insulin infusion—this is critical to prevent recurrence of ketoacidosis and rebound hyperglycemia. 1, 2

Once DKA resolved and patient can eat:

• Start multiple-dose regimen with combination of rapid-acting and long-acting insulin 1, 2
• Continue IV insulin for 1-2 hours after subcutaneous insulin given 1
• Estimate total daily requirement at 0.3-0.4 units/kg/day, with half as basal and half as prandial coverage 6

Special Considerations for This Patient

Lung Cancer and Immunotherapy

• If receiving immune checkpoint inhibitors (nivolumab, pembrolizumab), consider checkpoint inhibitor-associated diabetes mellitus (CIADM) 6, 7
• CIADM presents with rapid-onset insulin deficiency requiring permanent insulin therapy 6
• Check C-peptide and anti-GAD antibodies if immunotherapy-related DKA suspected 7
• Urgent endocrinology consultation recommended for any suspected CIADM 6

SGLT2 Inhibitor Risk

• Discontinue SGLT2 inhibitors immediately if present—do not restart until 3-4 days after metabolic stability achieved 2, 3
• SGLT2 inhibitors can cause euglycemic DKA (normal glucose with ketoacidosis), which is easily missed 4, 3
• Elderly patients on SGLT2 inhibitors are at higher risk for euDKA, especially with dehydration or acute illness 3

Infection Screening

• Infection is the most common DKA precipitant 2, 5
• Lung cancer patients are immunocompromised and at higher infection risk 2
• Obtain chest X-ray given lung cancer history and administer appropriate antibiotics if infection confirmed 1, 2

Common Pitfalls to Avoid

• Stopping IV insulin without prior basal insulin administration causes DKA recurrence—this is the most common error 1, 2
• Starting insulin before correcting severe hypokalemia (K+ <3.3 mEq/L) can cause fatal arrhythmias 1, 2
• Stopping insulin when glucose normalizes before ketoacidosis resolves perpetuates acidosis 2
• Failing to add dextrose when glucose falls below 250 mg/dL leads to hypoglycemia 2
• Inadequate potassium monitoring and replacement is a leading cause of DKA mortality 2
• Premature transition to subcutaneous insulin without 2-4 hour overlap causes rebound hyperglycemia 1, 2

Alternative Approach for Mild-Moderate Uncomplicated DKA

If this patient is hemodynamically stable, alert, and has mild-moderate DKA:

• Subcutaneous rapid-acting insulin analogs combined with aggressive fluid management are equally effective, safer, and more cost-effective than IV insulin 1, 2, 5
• This requires adequate fluid replacement, frequent glucose monitoring, and treatment of concurrent infections 2
• However, continuous IV insulin remains standard of care for critically ill or mentally obtunded patients 2, 5